The invention relates to the field of inertial navigation systems and relates in particular to an apparatus calculating the angular position (attitude) and spatial position of a flying device (missile, projectile, drone, etc) or non-flying device to be determined on-board relative to a ground reference frame.
Classically, inertial systems used in missiles and projectiles are based on the integration of rotational speeds and accelerations measured in flight. For accuracy, these methods require high-quality, and hence expensive, on-board sensors to limit noise and measurement bias. This is because successive integrations cause substantial drift in attitude angles and spatial coordinates.
On this subject, US Patent Application 2005/0240347 is known, which describes an inertial system having, in particular, a three-axis magnetometer, a three-axis gyrometer, and a three-axis accelerometer which operates in two modes:                a “static” mode that involves measuring the direction of gravity,        a more complex “dynamic” mode which begins by estimating errors, particularly those due to the drift of the various sensors before making a prediction, which is incompatible with real-time operation unless highly sophisticated sensors with very low drift, but also low reliability, are used.        